1. Field of the Industrial Application
This invention relates to an electrical coil unit which is formed by winding a conductor on a bobbin of resin.
2. Description of the Prior Art
A conventional electrical coil unit, as shown in FIG. 2, comprises: a bobbin 1 in the form of a cylinder or rectangular parallelepiped which is made of non-magnetic material such as resin; two flanges 3 on both sides of the winding portion 7 of the bobbin 1; and a coil winding 5 wound on the winding portion 7 between the flanges 3. Two end portions of the coil winding 5, namely, the two leaders are extended through one or both of the flanges 3. The leaders 10 have the end portions 12 of a predetermined length, respectively, from which the insulating film is removed (hereinafter referred to as "bare end portions 12", when applicable). More specifically, the bare end portion 12 of each of the leaders 10 is formed by starting the removal of the insulating film from the point on the leader 10 which is at a predetermined distance from the region of the winding portion 7. The bare end portions 12 are connected to input and output terminals.
The coil unit is manufactured for instance as follows: The insulating film is stripped from the leader 10 extended from the winding starting end of the coil winding 5, to provide one of the bare end portions 12. Thereafter, the coil winding 5 is wound on the winding portion 7 of the bobbin. The leaders of the coil winding 5 are extended through the flange or flanges 3. Under this condition, the insulating film is removed from another leader 10 extended from the winding finishing end of the coil, to provide the other bare end portion 12, and the leader 10 is cut as required.
In the above-described coil unit, the bare end portions 12 are set apart from the flanges 3 so that they may not go into the region of the winding portion 7. However, since forming the coil winding 5 on the bobbin 1 and removing the insulating film from the leaders 10 of the coil winding 5 are automatically carried out by the machines, the winding of the coil winding 5 by the winding machine may be fluctuated, with the result that the bare end portions 12 of the leaders 10 may go into the region of the winding portion 7.
If, in this case, the insulating film of the coil winding 5 wound on the winding portion 7 has pin holes, then short circuits may occur with the coil winding 5; that is, the coil unit may not work correctly.